Microdisplay projection systems typically employ a transmissive or a reflective microdisplay imager, commonly referred to as a light valve or light valve array, which imposes an image on an illumination light beam. One of the important advantages on reflective light valves over transmissive light valves is that reflective light valves permit controlling circuitry to be placed behind the reflective surface, and more advanced integrated circuit technology is available because the substrate materials are not limited by their opaqueness.
Reflective liquid-crystal-on-silicon (LCOS) imagers rotate the polarization of incident light. Thus, polarized light is either reflected by the imager with its polarization state substantially unmodified, or with a degree of polarization rotation imparted to provide a desired grey scale. Accordingly, a polarized light beam is generally used as the input beam for reflective LCOS imagers, while a polarizing beam-splitter (PBS) is typically employed for splitting the incoming light beam to two polarized light beams in orthogonal polarization states.
Widely used for various portable and handheld projection display applications, a typical optical projection engine device 500 employs one LCOS modulation imager 110 and one PBS 200 in the simplest but most compact configuration, illustrated in FIG. 1. One of the most obvious drawbacks of this Cartesian optical projection engine device 500, comprising the single PBS 200 and the single modulation imager 110, is that only limited portion of illumination light in one polarization state is used for illuminating the modulation imager 110 and therefore, after modulation and reflection by the modulation imager 110, total illumination projected through the projection lens system 300 onto a projection screen 390 is limited. Besides, the PBS 200 in prior art is made of a multilayer film which often contains organic species or is made of polymeric materials and vulnerable to intensive visible and infrared radiation. Besides, such multilayer film has a narrow optical receiving angle of polarization than the wire grid polarizer.